1. Field of the Invention
The present invention relates to positioning of a roller unit in an image forming apparatus including an image bearing member unit in which a rotating image bearing member is provided and the roller unit in which a roller substantially parallel to a direction perpendicular to a rotating direction of the image bearing member is provided.
2. Related Background Art
Members that constitute an image forming apparatus are often integrated as a unit for easy maintenance.
Japanese Patent Application Laid-Open No. 2004-53819 discloses an example of an image forming apparatus including members as a unit.
In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-53819, for an image bearing member unit to be easily mountable to or detachable from a chassis of the image forming apparatus in a direction substantially parallel to a direction perpendicular to a rotation axis of the image bearing member.
A method shown in FIG. 6 has been used as a method for positioning an image bearing member unit A and a roller unit 5 in an image forming apparatus having a detachably mountable image bearing member unit as described above. For the image bearing member unit A to be mountable to or detachable from a chassis of the image forming apparatus in a direction perpendicular to a rotation axis of an image bearing member (the direction of arrow X in FIG. 6), a part to be supported 47 at one end part side (the side of a front side plate 101) of a shaft 45 of an image bearing member 4 is positioned with respect to a plate 81 of the image bearing member unit A in the direction of arrow X in FIG. 6.
On the other hand, a part to be supported 48 a at the other end part side (the side of a rear side plate 102) of the shaft 45 of the image bearing member 4 is positioned with respect to the rear side plate 102 of the chassis of the image forming apparatus for positioning the image bearing member 4 in the chassis of the image forming apparatus.
A roller unit 5 in which a roller member 51 is provided is positioned so that a positioning member 57 of the roller unit 5 comes into contact with a member 87 provided on the front side plate 101 of the chassis of the image forming apparatus on the side of the front side plate 101, and a positioning member 58 of the roller unit 5 comes into contact with a member 103 provided on the rear side plate 102 of the chassis of the image forming apparatus on the side of the rear side plate 102, and a distance between the shaft 45 of the image bearing member 4 and a shaft 51a′ of the roller 51 is a desired distance.
However, when the roller unit is positioned by the above described method, position accuracy of the roller with respect to the image bearing member on the side of the front side plate 101 is poorer than positing accuracy of the roller with respect to the image bearing member on the side of the rear side plate 102, and the distance between the image bearing member and the roller on the side of the rear side plate 102 is not the desired distance, thereby generating a defective image.